Identifying global synchronies in marine zooplankton populations: issues and opportunities

Analyses of the influences of climate variability on local zooplankton populations and those within ocean basins are relatively recent (past 5–10 years). What is lacking are comparisons of zooplankton population variability among the world's oceans, in contrast to such global comparisons of fish populations. This article examines the key questions, capabilities, and impediments for global comparisons of zooplankton populations using long-term (>10 year) data sets. The key question is whether global synchronies in zooplankton populations exist. If yes, then (i) to what extent are they driven by “bottom-up” (productivity) or “top-down” (predation) forcing; (ii) are they initiated by persistent forcing or by episodic events whose effects propagate through the system with different time-lags; and (iii) what proportion of the biological variance is caused directly by physical forcing and what proportion might be caused by non-linear instabilities in the biological dynamics (e.g. through trophodynamic links)? The capabilities are improving quickly that will enable global comparisons of zooplankton populations. Several long-term sampling programmes and data sets exist in many ocean basins, and the data are becoming more available. In addition, there has been a major philosophical change recently that now recognizes the value of continuing long-term zooplankton observation programmes. Understanding of life-history characteristics and the ecosystem roles of zooplankton are also improving. A first and critical step in exploring possible synchrony among zooplankton from geographically diverse regions is to recognize the limitations of the various data sets. There exist several impediments that must be surmounted before global comparisons of zooplankton populations can be realized. Methodological issues concerned with the diverse spatial and temporal scales of “monitored” planktonic populations are one example. Other problems include data access issues, structural constraints regarding funding of international comparisons, and lack of understanding by decision-makers of the value of zooplankton as indicators of ecosystem change. We provide recommendations for alleviating some of these impediments, and suggest a need for an easily understood example of global synchrony in zooplankton populations and the relation of those signals to large-scale climate drivers

Spatial dependence of calanoid copepod diversity in the North Atlantic Ocean

International audienceEcosystems are fundamentally structured in space and time, The identification and quantification of scales of variability has occupied a central place in ecology for several decades. This paper examines spatial changes in the diversity of calanoid copepods and its regional dependence in the North Atlantic Ocean at diel, seasonal and interannual scales. Point cumulative semi-variograms, initially proposed for geological purposes, are described and intensively used to understand the relationships between diversity and its spatial scales of variability, A map of the mean spatial dependence in calanoid diversity is then proposed and diel and seasonal changes examined. This shows that diversity changes at small spatial scales over the European shelf seas. In oceanic areas, diversity changes at large spatial scales in both the subarctic and the northern boundary of the subtropical gyres. Low spatial scales of variability are detected in the Gulf Stream extension, in the path of the North Atlantic Current and west of Europe. A negative relationship between diversity and its spatial dependence is found in almost all the oceanic regions. This relationship is constant at all temporal scales, At an annual scale, relationships between diversity, spatial dependence and climatic indices have been investigated, Some links have been detected but both the intensity and the sign of these relationships vary greatly in space. The regime shift that took place in the North Sea after 1988 involved a sharp change in the diversity of calanoid copepods and a significant strengthening in the contrast between the neritic and oceanic spatial dependence

Influence of the northeastern Atlantic oceano-meteorological variability on the northern hake ("merluccius merluccius"). Analysis of the 1978-2006 period

316 p. : il., graf., map.[EUS]Tesi honetan iparraldeko legatz europarraren populazio-dinamika ikertu eta inguruneko parametroen eragina aztertu da 1978-2006 artean. Gainera, bizitzako lehen faseetan legatzaren kalteberatasunaren atzean dauden kausak zeintzuk diren ere identifikatu dira. Komertzialki hain espezie garrantzitsua izanik, arrantzaren eragina nabaria da legatzaren biomasak 80ko hamarkadan jasandako jeitsiera zorrotzean. Legatz europarraren denboran zeharreko erreklutamenduak dentsitatearekiko menpekotasuna erakutsi du, gurasoen biomasak urteroko erreklutamenduan duen garrantzia azpimarratuz. Hala ere, ezin da ziurtatu stock-reklutamendu erlazio horrek Ricker itxura hartzen duenik, datu falta baitago, batik bat, stock-aren balio baxuetarako. Bestalde, inguruko aldakortasun ozeano-klimatikoak zeresan handia dauka legatzaren erreklutamenduaren arrakastan. Ikusi da legatzaren bizitzako lehen faseetan tenperatura epelagoa izatea mesedegarri izan daitekeela legatzarentzat (bai kondizio egokien eremua/sasoia zabaltzen delako, edota hazkuntza-tasa altuagoengatik). Gainera, kostaranzko garraioak fase sentikorren dispertsioa saihestuko luke, eta, errute-eremuetatik hazkuntza-eremuetarako garraioa lagunduko luke. Baldintza egoki hauek garrantzi handikoak izan dira legatzaren erreklutamenduaren arrakasta ziurtatzeko, batik bat, legatzaren biomasa balio izugarri baxuetan aurkitu zen kasuan. Amaitzeko, ikerketa honen emaitzek iradokitzen dute erregimen-aldaketa ekologiko bat gertatu zela Atlantikoko ipar-ekialdeko plataforma kontinentalean 1988/89 urteetan. Erregimen-aldaketa hau eskala globalean ez ezezik (NAO, Golkoko korronte indizea eta Ipar Hemisferioko tenperaturen anomaliak), eskualde-mailan ere gertatu zen (Atlantikoko ipar-ekialdeko klimatologia eta Zelta itsasoko kopepodoen aldakortasuna). Legatzaren erreklutamendu-arrakastan gertatutako aldibereko aldaketa kontuan izanik, ondorioztatu da sasoi horretako ingurunea legatzarentzat onuragarria dela.[ES]En esta tesis se ha estudiado la dinámica poblacional del stock del norte de la merluza europea, así como la influencia de los parámetros ambientales durante el periodo 1978-2006. Además, se han identificado las variables que afectan la vulnerabilidad de lo estadios tempranos de la merluza. En una especie comercial como la merluza, la presión pesquera ha hecho que la biomasa de esta especie haya disminuido significativamente en la década de los 80. El reclutamiento de la merluza europea ha mostrado ser dependiente a la densidad del stock, y, esto subraya, la importancia que la biomasa parental tiene en el reclutamiento anual. Sin embargo, no se puede demostrar que esa relación stock-reclutamiento siga el modelo Ricker, debido a la falta de datos, sobre todo para valores bajos de biomasa. Por otra parte, la variabilidad océano-climática tiene mucha importancia en el éxito del reclutamiento de la merluza. Se ha demostrado que en los primeros estadios de vida de la merluza, una temperatura más cálida puede ser favorable para esta especie (se extiende el área/periodo óptimo, o/y las tasas de crecimiento son mayores). Asimismo, el transporte hacia la costa evitaría la dispersión de huevos y larvas, y favorecería el transporte de estas fases vulnerables desde las áreas de desove hasta las zonas de crecimiento. Estas condiciones favorables son de gran importancia a la hora de asegurar el éxito en el reclutamiento de la merluza, sobre todo cuando la biomasa de la merluza se encuentra en valores extremadamente bajos. Finalmente, los resultados de este trabajo sugieren un cambio de régimen ecológico en la plataforma continental del Atlántico noreste en los años 1988/89. Este cambio de régimen se detectó no sólo a escala global (NAO, el índice de la corriente del Golfo y anomalías de temperatura en el Hemisferio Norte), sino también a nivel regional (climatología del Atlántico noreste y variabilidad en la abundancia de copépodos en el mar Celta). Considerando que el cambio en el éxito del reclutamiento tuvo lugar en sincronía con el cambio ecológico, se concluye que el entorno de la merluza se volvió favorable para su supervivencia.The work carried out in this Dr. Philos Thesis has been developed in AZTI-Tecnalia and it has been financed by: Fundación Centros Tecnológicos Iñaki-Goenaga-k emandako “Oceanografía y recursos marinos” doktoretza-aurreko beka 2005-2009

Climate Change and Copepod Size Distribution: Comparison of Two Coastal Long-Term Series in the Western Mediterranean Sea

This thesis was aimed at investigating long-term dynamics of zooplankton communities in relation to climate change. It represents a pioneer study in comparing Mediterranean time series with a standardised methodology, i.e., the ZooScan, a digital imaging system for counting and sizing mesozooplankton from preserved samples. This study has proven that copepod size spectra (i.e., histogram of organisms arranged by size classes) obtained with the ZooScan is a powerful synthetic index to monitor changes in the pelagic system. Copepod abundance and size spectra were analyzed in the zooplankton time series conducted at stn MC (Gulf of Naples, Tyrrhenian Sea) and Point B (Villefranche Bay, Ligurian Sea) for the years 1986-2005 and 1974-2003, respectively. In both time series, the proportion of large individuals in the copepod community increased over the years, with a shift in the early 1990s at stn MC and in 1987 at Point B. In both cases, the 1990s copepod reproduction might have decreased due to earlier and stronger stratification driven by rising temperature. At stn MC, the shift to dominance of small phytoplankton cells in the 1990s seemed to be the direct cause. At Point B, in addition to the detrimental effect of earlier stratification in the 1990s, the 1980s seemed to be very productive due to strong winter convection driven by cool salty winters. High salinity was related to low winter atmospheric pressure linked to the North Atlantic Oscillation (+ winter NAO). In both locations, the frequency of occurrence of typical offshore species increased over the years, suggesting changes in coastal-offshore interactions. Mechanisms controlling the copepod communities in both sites seem to be different. Stn MC has a more coastal character than Point B and thus the former is more affected by local conditions as terrestrial nutrient inputs. At Point B, stratification-destratification dynamics seem to control production

Global biogeographical patterns of plankton in response to climate change

226 p.La evidencia científica es abrumadora: el cambio climático está ocurriendo y gran parte delcambio es un resultado directo de la actividad humana. Las observaciones demuestran quedurante los últimos 40 años el 84% del total del calentamiento de la tierra ha ido a calentarlos océanos, alterando así los sistemas naturales que habitan en él. Se han observadoincrementos en la temperatura superficial del agua (0.11°C década-1) entre 1971-2010,incrementos en la velocidad del viento y frecuencias de tormentas, cambios en la circulaciónoceánica, estructura vertical y aporte de nutrientes, acidificación de los océanos, así como unincremento del nivel del mar de en torno a unos 15 cm durante el último siglo.Los impactos del cambio climático afectan a todo el ecosistema pelágico, desde el planctonhasta niveles tróficos superiores. Estos impactos generan una serie de respuestas en lasespecies como por ejemplo cambios latitudinales en los rangos de su distribución, cambios enlos ciclos estacionales, así como cambios en la abundancia y estructura de las comunidades.Particularmente en el plancton, se ha demostrado que los cambios en la biogeografía son delos más grandes y rápidos observados hasta ahora. Por ello, el cambio climático puede darlugar a extinciones o invasiones locales en las especies, que repercuten en los patrones debiodiversidad y causan desajustes tróficos. En esta serie de respuestas, la dispersión de lasespecies, con el simple hecho de desplazarse desde un hábitat a otro, es un proceso clave;determina el ritmo de extensión de una población y permite el flujo genético entre ellas, locual es fundamental en los procesos de adaptación a condiciones climáticas cambiantes. Deeste modo, la resiliencia o vulnerabilidad de las comunidades marinas frente al cambioclimático dependerá de la capacidad de adaptación o dispersión de cada especie así como desu grado de conectividad.Comprender, predecir y gestionar las respuestas de la biodiversidad al cambio climático exigeuna consideración completa de los patrones biogeográficos de las especies, que estándefinidos por su nicho ecológico y características de dispersión, y cómo estas característicaspueden cambiar debido al cambio climático. Los estudios sobre el zooplancton, losprincipales productores secundarios del océano y el principal grupo objetivo de esta tesis,pueden mejorar el conocimiento existente sobre cómo los ecosistemas marinos estánrespondiendo al cambio climático. El zooplancton es particularmente sensible a los cambiosambientales a corto plazo, ya que tanto su dinámica poblacional como sus procesosfisiológicos están altamente ligados a la temperatura. Debido a esta sensibilidad, lascomunidades de zooplancton pueden utilizarse como indicadores para evaluar la salud de losecosistemas marinos, y la variación de sus patrones de distribución puede proporcionarinformación valiosa sobre los cambios físicos que ocurren en los océanos globales.Nuestro estudio tiene como objetivo analizar los patrones biogeográficos del plancton aescala global y su respuesta frente al cambio climático. Los estudios biogeográficos requierenun profundo conocimiento del nicho ecológico de las especies, definido aquí como el rango detolerancia de cada especie a un set de variables ambientales que limitan su distribución. Estatesis pretende estudiar los patrones macro-ecológicos del plancton en varias escalas: desdelos genes hasta las comunidades, desde zonas costeras hasta el océano global, desdetendencias históricas hasta proyecciones futuras. Para tal fin, hemos aplicado técnicas ymodelización estadística en bases de datos globales.Aztitecnali

Marine species and climate change: using modelling techniques to investigate effects on species distributions

Anthropogenic climate change is one of the main challenges affecting the globe, with particular implications for the oceans. Marine climate change research has moved forward rapidly in recent years, and a range of physical model outputs are available that can be used by ecologists to help predict how species might be affected into the future. Policy makers require a level of understanding of how certain species and their ranges might change so that they can respond with sustainable management actions. This thesis aims to make use of a number of modelling techniques to explore implications of past and future conditions for marine species, and to appraise those tools that can be used under differing circumstances. Policy questions are answered relating to changes in the abundance and distribution of marine species. The links between historical climatic conditions and Barents Sea cod abundance are explored using Generalised Additive Models using data collected in the middle of the 20th century. This valuable historical data indicated that cod have temperature preferences and expand and shift their distributions based on environmental conditions. A simpler modelling technique is used to examine how oxygen conditions have changed in recent decades in the North Sea, how they might change in the future, and what implications this has for commercial fish species. The models show that oxygen conditions have improved recently and that they will not decrease to levels that result in large negative effects in the coming century. Species distribution modelling using a combination of global and downscaled model outputs shows that the UK will become more suitable for some non-native and harmful algal species in the 21st century, and less suitable for others. The model outputs contribute to the understanding of climate change effects and development of management tools to ensure the resilience of marine ecosystems into the future.Centre for Environment, Fisheries and Aquaculture Science (Cefas)Department for Environment, Food and Rural Affairs (Defra

Mesozooplankton of the scotia sea: present, past and future

The potential impact of global warming on plankton populations and processes in the Southern Ocean is cause for concern. Greatest attention has concentrated on Antarctic krill, a keystone macroplankton species and currently the object of a commercial fishery. This thesis focuses on the mesozooplankton component of the zooplankton, in particular the Copepoda. These crustaceans are major secondary producers and are important dietary items for mesopelagic fish as well as being major recyclers of particulate carbon and nutrients. The balance between krill and copepods fundamentally influences the nature of ecosystem function, particularly with regard to carbon export and remineralization. In this synthesis of 18 years of research, summarised in eight papers, I address the question of whether there have been shifts in the distribution and community structure of mesozooplankton in the Scotia Sea over the last 70 years. Net samples obtained between 1995 and 2009 were compared with samples collected during the 1920s-1930s by the Discovery Investigations. Taking into account differences in net design between eras, no differences in overall abundances or community composition were initially apparent. Despite a median increase of 0.74oC in sea surface temperature since the 1930s, plankton distributions from contemporary sampling were geographically similar. However, further analysis showed that although ranked abundances were comparable between eras, three of the four biomass dominant copepods had increased in absolute abundance by ~20- 55% during contemporary times. Reasons for this are considered to be linked to changes within the food web, driven by decreasing krill abundance as a result of warming-induced habitat loss and the commercial exploitation of whales. Future investigations into spatial distributions and trophic overlap between krill and copepods, as well as renewed efforts in modelling the ecosystem effects consequent upon the harvesting of whales, are recommended